Material characterization systems using electromagnetic waves are available to measure certain properties of a material. The reflectivity, transmissivity, and absorptivity of electromagnetic waves impinging upon a sample of a material can be measured to determine important attributes of such material, including surface characteristics, internal homogeneity, insertion loss, dielectric permittivity, loss tangent, shielding effectiveness, and even manufacturing defects. However, where the measurement area of the sample under evaluation is near an edge of the material, the electromagnetic waves interact with the edge of the material and may corrupt the measurements.
Edge treatment systems and methods exist for mitigating the effects of the interaction of electromagnetic waves with the edge of a material. In particular, attenuation of the reflection of electromagnetic radiation in a given frequency range by means of an edge treatment based on a structure of properly-spaced long strips of electrically loaded conductive material and a dielectric spacer has been addressed in the prior art, as described in U.S. Pat. No. 6,184,815 to Carlson. However, this treatment is based on forming a transmission line between these strips and the treated material to match the impedance of the material to free space. Thus, the effectiveness of this approach is limited to treating relatively high-conductive materials, requires a spacing between the edge treatment structure and the treated material, and may not be suitable for small-size samples.
Primarily, the applications of material evaluation systems based on propagating electromagnetic waves include material characterization, calibration, and general purpose measurements. Therefore, edge-diffraction of the electromagnetic waves impinging upon a sample under test may lead to inaccuracies that render measurements worthless. As a result, in order to minimize these edge effects, a number of limitations may be imposed on the capabilities of the material evaluation system, such as the frequency range of operation, the size and area of the sample under test, the sophistication and complexity of the components of the system, and the quality control of a material under production. Thus, an edge treatment technique that allows accurate measurements of a material to overcome these limitations are key in terms of costs and operational functionality of users.
Currently, there is no well-established method of accurately characterizing a sample of a material under evaluation near the edges of such material, using electromagnetic waves. Such solutions are particularly lacking in industrial applications wherein the quality of a material under production must be monitored continuously to guarantee a level of performance from edge-to-edge. As a consequence, multiple material evaluation methods may be necessary to implement or a substantially lower productivity may result. Furthermore, lower product quality and larger tolerances in the performance characteristics of a material may be expected. Likewise, the cost of production of high-quality material may significantly increase.
Previous efforts have been made to suppress diffraction of electromagnetic waves from an edge, as described in U.S. Pat. No. 8,035,568 to Diaz et al., U.S. Pat. No. 5,963,176 to Solheim et al., and U.S. Pat. No. 5,298,911 to Li. However, these efforts have faced certain challenges and limitations for material evaluation applications. In particular, attempts made to reduce edge-diffraction from antenna surfaces have been generally unsuccessful for material evaluation applications because of the narrow frequency bandwidth, large size, or the need to physically modify or have a relatively high-conductive material under test. Such previous efforts have been particularly lacking in the evaluation of a small-size sample of a material where all edges of the sample may interact with the electromagnetic waves used during measurements.
Thus, there remains a need in the art for improved systems and methods for treating the edges of a material under evaluation, through measurements of propagating electromagnetic waves, that avoid the problems of prior art systems and methods.